<!DOCTYPE html>
<html>

<head>
    <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
    <link href="css/theme-classic-all.css" rel="stylesheet" />
    <script type="text/javascript" src="js/ext-all.js"></script>
    <script type="text/javascript">
        Ext.onReady(function() {
            Ext.create('Ext.panel.Panel', {
                title: 'Hello',
                 width: 200,
                 height: 300,
                 items: [{
                    xtype: 'button',
                     text: 'OK',
                     handler: function() {   
                        alert('I\'m a Button'); 
                    }
                }, {
                    xtype: 'panel',
                     html: 'I\'m a child Panel'
                }],
                renderTo: Ext.getBody()
            });
        });
    </script>
</head>

<body>

</body>

</html>